Modern data networks typically comprise a plurality of network devices, including network bridges, switches, and routers. Such devices often perform many modifications to data packets in the course of normal operations. Desired modifications to data packets may include, for example, adding data to a packet (e.g., adding an Ethertype tag), removing data from a packet, changing data in a packet (e.g., modification of the MAC DA and SA), or prepending data to the packet (e.g., adding a header).
Network devices commonly implement packet modification capabilities through use of large memory buffers having the ability to temporarily store an entire data packet. In such devices, a data packet requiring modification is first stored in its entirety in a large memory buffer. Necessary changes to the data packet are then made within the memory buffer and, upon completion of all changes, the modified data packet proceeds from the memory buffer into the communication channel. While straightforward, this packet modification architecture results in substantial hardware costs associated with large memory buffers, as well as inherent system latencies caused by the need to buffer the entire packet during packet modification. Therefore, a flexible method for modifying a data packet without the need to buffer an entire packet during modification (i.e., near wire-speed modification) proves advantageous to efficient network device design.
Packet modification capabilities are often incorporated directly into network device hardware due to the operating speed benefits such a design offers. Present day network devices thus require either changing application-specific integrated circuits (i.e., ASICs) or redirecting data packets to higher-level software in order to modify data packets in a manner not anticipated in their original design. These changes can impact overall device performance and add significant network device latencies. Consequently, as new data network features are defined requiring the modification of packets in a manner not anticipated in a device's original design, it is desirable to develop a method for data packet modification allowing for implementation of new network features without requiring physical hardware changes or impacting overall device performance.
It is accordingly a primary object of the invention to allow for flexible near wire-speed modification of data packets within a data network after an original device design has been implemented, without the need for hardware changes or the redirection of packets to higher-level software to achieve packet modification.